Epoxy based balancing compound and method for balancing a rotor utilizing an ultraviolet-curable epoxy resin composition

ABSTRACT

A balancing compound comprising an epoxy resin, a photoinitiator in an effective amount to cure the resin at ambient temperatures upon the application of ultraviolet light (10 nm to 400 nm) of less than 40 watts per square centimeter in less than about 30 seconds, and a filler in an effective amount to give the compound a specific gravity above 1.1.

BACKGROUND OF THE INVENTION

The subject matter of the invention relates to epoxy resin compositionsand methods of balancing a rotor utilizing the same, and moreparticularly, to an ultraviolet light curable cross-linked epoxy resincomposition and a method for dynamically balancing motor armatures andother rotors by dynamically testing the rotors repeatedly and applyingan ultraviolet cured cross-linkable epoxy resin composition betweentests to achieve the balance required.

Rotors such as electric motor armatures have previously been balancedutilizing a two-part epoxy based composition which is applied to anarmature in a putty like consistency which is sufficiently tacky,adherent and cohesive to adhere to the armature during dynamic testingfor balance prior to curing, dynamically testing the rotor with thebalancing compound in position thereon, adjusting both the amount of thebalancing position and the position of the balancing compound on therotor to achieve the desired balance, and then curing the resin. SeeU.S. Pat. No. 3,939,020. This two-part epoxy composition includes onepart which includes the epoxy resin and another part which includes thecatalyst for curing the resin. Each part of the composition is storedseparately from the other part until ready for use. When balancing is tobe accomplished, the two parts of the composition are mixed in equalamounts by weight and the dynamic balancing of the armature is carriedout by the method above-described. After desired balancing is achieved,the balancing compound can be cured either by allowing the armature tostand at room temperature for a period of time or heating the rotor.

Single part epoxy balancing compounds have also been proposed that havea shelf life of about three months at ambient temperatures. Thesebalancing compounds can be utilized to balance motor armatures and otherrotors in a similar manner as above described except that curing may beachieved within a range from about six minutes to about three hours atelevated temperatures, for example, 45 minutes at 300° F. One example ofthese compositions are the BC motor balancing compounds by StarTechnology, Inc.

Both of these prior balancing compounds require a large amount of energyor a large amount of time to cure the epoxy balancing composition. Somerequire both. In the balancing compound of U.S. Pat. No. 3,939,020, thebalanced armature can be cured in about 20 minutes by heating thecompound to a temperature of about 200° F. In others, cure oventemperatures are used as high as 400° F. for four hours. In some cases,these temperatures for prolonged times can cause the motor armature todistort and be once again out of balance or can cause another portion ofthe armature to thermally degrade. In the specific instance ofarmatures, the copper windings can expand and relocate upon curing tocause the armature to be again out of balance.

Prior balancing compounds are used in pieces or lumps, and it has alwaysbeen a problem to thoroughly cure the balancing composition on the rotorin less than about four minutes. This is especially true with thosebalancing compounds which are heavily filled with mineral fillers whichare applied to highly conductive metals such as those which predominatein a motor armature. It is believed that this lack of deep section cureis due to the temperature gradient between the outside of the piece orlump of balancing compound and the inside of the piece or lump normallyexperienced when oven curing these compounds on an armature of highlyconductive metal. Some but not all of this deep cure problem can beovercome with catalysts.

Some manufacturers test armatures by spinning them at from about 2,000rpm to about 15,000 rpm at elevated temperatures from about 250° F. toabout 300° F. for about 30 seconds followed by balance tests. These spintests show failures when the balancing compound is not fully cured, orwhen the heat deformation temperature of the compound is sufficientlylower than the test temperature.

It is therefore highly desirable to provide an improved balancingcompound.

It is also highly desirable to provide an improved balancing compoundwhich is a single part epoxy based composition which can be applied toan armature in either a paste-like consistency or a putty-likeconsistency.

It is also highly desirable to provide an improved balancing compoundwhich can be provided in a single part epoxy compound which does notrequire mixing or formulation prior to use and has an appreciable shelflife.

It is also highly desirable to provide an improved balancing compoundwhich can be cured rapidly at room temperature such that the balancingcompound can be used on devices easily thermally degradable.

It is also highly desirable to provide an improved balancing compoundwhich can be thoroughly cured by exposure to ultraviolet light and/orheat in a relatively short time,

It is also highly desirable to provide an improved balancing compoundwhich remains in place upon the rotor during spin tests at elevatedtemperatures,

It is finally highly desirable to provide an improved balancing compoundwhich has all of the features above mentioned.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide an improvedbalancing compound,

It is also an object of the invention to provide an improved balancingcompound which is a single part epoxy based compound which can beapplied to an armature in either a paste-like consistency or aputty-like consistency,

It is also an object of the invention to provide an improved balancingcompound which can be provided in a single part epoxy compound whichdoes not require mixing or formulation prior to use and has anappreciable shelf life.

It is also an object of the invention to provide an improved balancingcompound which can be cured rapidly at room temperature such that thebalancing compound can be used on devices easily thermally degradable.

It is also an object of the invention to provide an improved balancingcompound which can be thoroughly cured by exposure to ultraviolet lightand/or beat in a relatively short time,

It is also highly desirable to provide an improved balancing compoundwhich remains in place upon the rotor during spin tests at elevatedtemperatures.

It is finally an object of the invention to provide an improvedbalancing compound which has all of the features above mentioned.

In the broader aspects of the invention, there is provided a balancingcompound comprising an epoxy resin, a photoinitiator in an effectiveamount to cure the resin at ambient temperatures upon the application ofultraviolet light (10 nm to 400 nm) of less than 40 watts per squarecentimeter in less than about 30 seconds, and a filler in an effectiveamount to give the compound a specific gravity above 1.1.

DESCRIPTION OF A SPECIFIC EMBODIMENT

The improved balancing compound of the invention is an epoxy resincomposition which can be effectively cured throughout by exposure toboth ultraviolet light and heat relatively quickly without experiencingsubstantial shrinking or weight loss. The composition is electricallyinsulative and bonds well to metals, other resinous materials, ceramics,and glasses.

The improved balancing compound of the invention comprises an epoxyresin in an amount of from about 13% to about 90% weight of the totalcompound. The epoxy resin component can comprise one or more epoxidicprepolymers. These prepolymers can be crosslinked when cured into asolid matrix through the epoxide groups of the polymer.

These epoxidic prepolymers can be combined with any number of (1)polyols to adjust molecular weight of the prepolymers and provide thedesired amount of crosslinking in the balancing compound, (2) aphotoinitiator in an effective amount capable of causing cationicpolymerization of the epoxy resin when the initiator is exposed tosufficient ultraviolet radiation or sufficient thermal energy, (3) aneffective amount of photosensitizer or pigment which causes thephotoinitiator to become more active when exposed to ultraviolet lightand sensitive to additional wavelengths of light which would normallyhave no effect on the photoinitiator, (4) an effective amount of fillerto raise the specific gravity of the balancing compound to a desiredspecific gravity, (5) an effective amount of wetting agent to insurethat the filler is wet by the resin and to minimize refraction andreflection of the ultraviolet light at resin/filler interfaces, (6) aneffective amount of a thixotrope to maintain the filler in a homogeneoussuspension with the resin, and (7) an effective amount of catalyst toinsure the desired cure rate.

Typical formulations of the improved balancing compound of the inventionare:

    ______________________________________                                                      PHR                                                             ______________________________________                                        Epoxy resin     100.0                                                         Polyol           0.0-100.0                                                    Photoinitiator  0.1-4.0                                                       Fillers          10-550                                                       Photosensitizers                                                                              0.0-5.0                                                       Wetting agent   0.01-1.0                                                      Catalyst        0.01-5.0                                                      ______________________________________                                    

The epoxy resin component of the improved balancing compound of theinvention is an epoxidic prepolymer or a combination of a plurality ofepoxidic prepolymers of any of the known monomeric, dimeric, oligomericor polymeric epoxy materials containing one or a plurality of epoxyfunctional groups. Preferably, they will be members of the classesdescribed chemically as (a) an epoxidic ester having two epoxycycloalkylgroups; (b) an epoxy resin prepolymer consisting predominately of themonomeric diglycidyl ether of bisphenol A; (c) a polyepoxidized phenolnovolak or cresol novolak; (d) a polyglycidyl ether of a polyhydricalcohol; (e) a diepoxide of a cycloalkyl or alkylcycloalkyl hydrocarbonor ether; (f) halogenated versions of any of the above; or (g) a mixtureof any of the foregoing. To save unnecessarily detailed description,reference is made to the Encyclopedia of Polymer Science and Technology,Vol. 6, 1967, Interscience Publishers, New York, pages 209-271.

Suitable commercially available epoxidic esters are3,4-epoxycyclohexylmethyl, 3,4-epoxycyclohexanecarboxylate (UnionCarbide ERL 4221, Ciba Geigy CY-179); as well asbis(3,4-epoxy-6-methylcyclohexylmethyl)adipate (Union Carbide ERL 4289);and bis(3,4-epoxycyclobexylmethyl)adipate (Union Carbide ERL 4299).

Suitable commercially available diglycidyl ethers of bispbenol-A areCiba Geigy Araldite 6010, Dow Chemical DER 331, and Shell Chemical Epon828.

A polyepoxidized phenol formaldehyde novolak prepolymer is availablefrom Dow Chemical as DEN 431 and 438, and a polyepoxidized cresolformaldehyde novolak prepolymer is available from Ciba-Geigy as Araldite538.

A polyglycidyl ether of a polyhydric alcohol is available fromCiba-Geigy, based on butane-1,4-diol, as Araldite RD-2; and from ShellChemical Corp., based on glycerine, as Epon 812.

A suitable diepoxide of an alkylcycloalkyl hydrocarbon is vinylcyclohexene dioxide, (Union Carbide ERL 4206); and a suitable diepoxideof a cycloalkyl ether is Bis(2,3epoxycyclopentyl)-ether, (Union CarbideERL 0400).

In a specific embodiment, the epoxy resin component is chosen from thegroup consisting of bisphenol A, bisphenol F, novolak, difunctionalglycidol ester, and cycloaliphatic based epoxy resins, organosiliconmonomers having a six member silicon dioxide ring, and sulfur containingmonomers having three and four member sulfur containing rings, andcombinations thereof. These latter two, while not technically epoxyresins, are included within the definition as that term is used in thisapplication and may be more clearly identified by the followingillustrations: ##STR1## In choosing the particular combination ofepoxidic prepolymers, the functionality of the resin to act as a binderto be crosslinked into a solid matrix should be taken intoconsideration. The bisphenol-A and bisphenol-F glycidol ether resins arerelatively brittle. In contrast, the cycloaliphatic resins arerelatively flexible. The novolak resins are relatively tacky and assistthe resins to adhere to the rotor being balanced. The tetraglycidolether of tetraphenolethane and the glycidated novolaks have a higharomatic ring content combined with polyfunctionality and providerelatively high thermal stability for higher temperature applications.Mono and difunctional diluents such as polyols, divinyl ethers, divinylesters and the like can alter the molecular weight of the resin asdesired.

The viscosity of the balancing compound and the flexibility thereof whencured can be adjusted by the choice of resin. Decreased viscosity andincreased flexibility result from additional divinyl ethers or divinylesters. Decreased flexibility results from the use of bisphenol-Aepoxides and epoxy novolaks.

Beside the novolak resins, the tackifiers and/or adhesion promotersinclude polyvinylethylether, polyvinylisobytalether, polyvinylbutyl,polyisobutylene, styrene/butydiencopolymer rubber, butyl rubber, vinylchloride/vinyl acetate copolymer, chlorinated rubbers, acrylic resintackifiers and aromatic, aliphatic and alkylcyclic petroleum resins.

The amount of polyol can increase or decrease the cross-linked densityof the reacted epoxy resin. Additionally, polyols (usually di ortrifunctional alcohols) can accelerate cure rates of the resin. Curerates may be increased by maintaining a Union Carbide R value between1.5 and 3, where: ##EQU1## The addition of polyols can also be used toadjust the viscosity of the balancing compound. Experience wouldindicate that the higher the R value, the harder the balancing compound,the lower the R value, the more adhesion and flexibility the balancingcompound will exhibit.

The polyols which can be used in combination with the epoxy resin ofthis invention can be produced in situ by polymerizing one or moreethylenically unsaturated monomers dissolved or dispersed in a basepolyol in the presence of a free radical catalyst. The production ofpolymer/polyols is more fully described in, for example, U.S. Pat. Nos.Re. 28,715, 29,118, U.S. Pat. No. 3,652,639, U.S. Pat. No. Re. 29,014,U.S. Pat. No. 3,950,317, U.S. Pat. Nos. 4,208,314, 4,104,236, 4,172,825and U.S. Pat. No. 4,198,488.

Substantially any of the polyether polyols previously used in the art tomake polymer/polyols can be used in this invention. Illustrative of thepolyether polyols useful in producing polymer/polyol compositions arethe polyhydroxyalkanes, the polyoxyalkylene polyols, or the like. Amongthe polyether polyols which can be employed are those selected from oneor more of the following classes of compositions, alone or in admixture:

(a) Alkylene oxide adducts of polyhydroxyalkanes;

(b) Alkylene oxide adducts of non-reducing sugars and sugar derivatives;

(c) Alkylene oxide adducts of phosphorus and polyphosphorus acids;

(d) Alkylene oxide adducts of polyphenols;

(e) The polyols from natural oils such as castor oil, and the like.

Illustrative alkylene oxide adducts of polyhydroxyalkanes include, amongothers, the alkylene oxide adducts of ethylene glycol, propylene glycol,1,3-dihydroxypropane, 1,3-dihydroxybutane, 1,4-dihydroxybutane,1,4-1,5-, and 1,6-dihydroxyhexane, 1,2-, 1,3-, 1,4-1,6-, and1,8-dihydroxyoctane, 1,10-dihydroxydecane, glycerol,1,2,4-trihydroxybutane, 1,2,6-trihydroxybexane, 1,1,1-trimethylolethane,1,1,1-trimethylolpropane, pentaerythritol, polycaprolactone, xylitol,arabitol, sorbitol, mannitol, and the like. A preferred class ofalkylene oxide adducts of polyhydroxyalkanes are the ethylene oxide,propylene oxide, butylene oxide, or mixtures thereof, adducts oftrihydroxyalkanes.

A further class of polyether polyols which can be employed are thealkylene oxide adducts of the non-reducing sugars, wherein the alkyleneoxides have from 2 to 4 carbon atoms. Among the non-reducing sugars andsugar derivatives contemplated are sucrose, alkyl glycosides such asmethyl glucoside, ethyl glucoside, and the like, glycol glycosides suchas ethylene glycol glucoside, propylene glycol glucoside, glycerolglucoside, 1,2,6-hexanetriol glucoside, and the like, as well as thealkylene oxide adducts of the alkyl glycosides as set forth in U.S. Pat.No. 3,073,788.

A still further useful class of polyether polyols is the polyphenols,and preferably the alkylene oxide adducts thereof wherein the alkyleneoxides have from 2 to 4 carbon atoms. Among the polyphenols which arecontemplated are, for example, bisphenol A, bisphenol F, condensationproducts of phenol and formaldehyde, the novolak resins, condensationproducts of various phenolic compounds and acrolein; the simplest memberof this class being the 1,1,3-tris(hydroxyphenyl)propanes, condensationproducts of various phenolic compounds and glyoxal, glutaraldehyde, andother dialdebydes, the simplest members of this class being the1,1,2,2,-tetrakis(hydroxyphenol) ethanes, and the like.

The alkylene oxide adducts of phosphorus and polyphosphorus acids areanother useful class of polyether polyols. Ethylene oxide,1,2-epoxypropane, the epoxybutanes, 3-chloro-1,2-epoxypropane, and thelike are preferred alkylene oxides. Phosphoric acid, phosphorus acid,the polyphosphoric acids such as tripolyphosphoric acid, thepolymetaphosphoric acids, and the like are desirable for use in thisconnection.

The polyether polyols employed can have hydroxyl numbers which vary overa wide range. In general, the hydroxyl numbers of the polyols employedin the invention can range from about 15, and lower, to about 900, andhigher. The hydroxyl number is defined as the number of milligrams ofpotassium hydroxide required for the complete neutralization of thefully phthalated derivative prepared from 1 gram of polyol. The hydroxylnumber can also be defined by the equation: ##EQU2## where

OH=hydroxyl number of the polyol;

f=functionality, that is, average number of hydroxyl groups per moleculeof polyol; and

m.w.=molecular weight of the polyol.

The most useful polyols include glycols and both aliphatic and aromatichydroxyl compounds containing 2 or more hydroxyl groups, for exampleethylene glycol; glycerin; pentaerythrytol; 1,1,1-trimethylol ethane;1,1,1- trimethylol propane; zorbitol; manitol; dipentaerythitol; anda,ω-aliphatic hydrocarbon diols having four to five carbon atoms; cyclicglycols; hydroquinone dibetahydroxy ethyl ether; 1,4-cyclohexanedimethylol; polyethylene glycol; polytetramethylene oxide glycol; andcombinations thereof. Examples of the aliphatic diols are 1,4 butanediol; 1,5 pentane glycol; neopenthylene glycol; 1,4-butene-2-diolpropylene glycol; and combinations thereof. Examples of the cyclic diolsare 2,2,4,4-tetramethyl-1,3-cyclobutane diol, andtris(2hydroxyethyl)isocyanurate and combinations thereof; ethyleneglycol, diethyleneglycol, the poly(oxypropylene)glycols, triols andhigher functionality polyols. These polyols also includepoly(oxypropylene-oxyethylene)polyols; however, desirably, theoxyethylene content should comprise less than 80% of the total andpreferably less than 60%.

The ethylene oxide when used can be incorporated in any fashion alongthe polymer chain. Stated another way, the ethylene oxide can beincorporated either in internal blocks, as terminal blocks, or may berandomly distributed along the polymer chain.

As is well known in the art, the polyols that are most preferred hereincontain varying small amounts of unsaturation. Unsaturation in itselfdoes not affect in any adverse way the formation of the coatingcompositions in accordance with the present invention. It should beappreciated that a blend or mixture of more than one base polyol can beutilized, if desired, to form the polymer/polyol.

Suitable commercially available blended or mixed organic polyols are thepolycaprolactone polyols such as TONE-0200 and TONE-0305 from UnionCarbide Corporation, the dihydroxy functional polytetramethylene oxidepolyols such as Polymeg 650, 1000 and 2000 from Quaker Oats Company,polyether polyols capped with ethylene oxide such as propylene oxidepolyols capped with ethylene oxide, e.g., E-480, E-474, NIAX Polyol11-27 and NIAX Polyol 11-34 from Union Carbide Corporation, and ofcourse the ethylene oxide and propylene oxide adducts including ethyleneglycol, diethylene glycol, the poly(oxyethylene)glycols, thepoly(oxypropylene glycols, triols and higher functionality polyols suchas LHT-67, LHT-112 and LG-56 from Union Carbide Corporation. Thesepolyols also include poly(oxypropylene-oxyethylene)polyols; however,desirably, the oxyethylene content should comprise less than 80% of thetotal and preferably less than 60%.

The ethylene oxide when used can be incorporated as internal Blocksalong the polymer chain. As is well known in the art, the polyols thatare preferred herein contain varying small amounts of unsaturation.Unsaturation in itself does not affect in any adverse way the balancingcompound in accordance with the present invention.

Other representative examples of suitable blended or mixed organicpolyols that may be employed in minor amounts in the balancing compoundof this invention include copolymers of hydroxypropyl and hydroxyethylacrylates and methacrylates with other free radical-polymerizablemonomers such as acrylate esters, vinyl halides, vinyl acetate, orstyrene; copolymers containing pendent hydroxy groups formed byhydrolysis or partial hydrolysis of vinyl acetate copolymers,polyvinylacetal resins containing pendent hydroxyl groups; modifiedcellulose polymers such as hydroxyethylated and hydroxypropylatedcellulose; hydroxy terminated polyesters and hydroxy terminatedpolyalkadienes. The polyester polyols are the reaction products ofpolyfunctional organic carboxylic acids and polyhydric alcohols andinclude, for example, poly(hexamethylene adipate), poly(ethyleneadipate), poly(butylene adipate) and the like. Many of these organicpolyols can be prepared by conventional methods and are commerciallyavailable from a number of manufacturers such as polyviylacetal resinscommercially available from Monsanto Chemical Company as Butvat B-72A,B-73, B-76, B-90 and B-98 and as Formvar 7/70, 12/85, 7/95S, 7/95E,15/95S and 15/95E; an aliphatic polyester diol commercially availablefrom Rohm and Haas as Paraplex U-148; saturated polyester polyolscommercially available from Mobay Chemical Company as Multron R-2,R-12A, R-16, R-18, R-38, R-68, and R-74; a hydroxypropylated cellulosehaving an equivalent weight of approximately 100 commercially availablefrom Hercules, Inc. as Klucel E, and a cellulose acetate butyrate esterhaving a hydroxyl equivalent weight of approximately 400 commerciallyavailable from Eastman Kodak as Alcohol Soluble Butyrate.

The polycaprolactone polyols, alone or in admixture, that can be used toprepare the balancing compound of this invention include any of theknown polycaprolactone polyols that are commercially available. Thepolycaprolactone polyols are produced by the catalytic polymerization ofan excess of lactone and an organic polyfunctional initiator having atleast two reactive hydrogen atoms. The organic functional initiators canbe any polyhydroxyl compound as is shown in U.S. Pat. No. 3,169,945.Illustrative thereof are the diols such as ethylene glycol, diethyleneglycol, triethylene glycol, 1,2-propylene glycol, dipropylene glycol,1,3-propylene glycol, polyethylene glycols, polypropylene glycols,neopentyl glycol, 1,4-butanediol, poly(oxyethyleneoxypropylene)glycols,and similar polyalkylene glycols, either blocked, capped or heteric,containing up to about 40 or more alkyleneoxy units in the molecule,3-methyl-1-5 pentanediol, cyclohexanediol,4,4'-methylene-bis-cyclobexanol, 4,4'-isopropylidene-bis-cyclohexanol,xylenediol, 2-(4-hydroxymethylphenyl)ethanol, 1,6-hexanediol and thelike; triols such as glycerol, trimethylolpropane, 1,2,6-hexanetriol,triethanolamine, triisopropanolamine, and the like; tetrols such aserythritol, pentaerythritol, dipentaerythritol, sorbitol,N,N,N'-N'-tetrakis(2-hydroxyethyl)ethylene diamine, and the like.

When the organic functional initiator is reacted with the caprolactone areaction occurs that can be represented in its simplest form by theequation: ##STR2## In this equation the organic functional initiator isthe R"(OH)_(x) compound and the caprolactone is the ##STR3## compound;this can be epsilon caprolactone itself or a substituted caprolactonewherein R' is an alkyl, alkoxy, aryl, cycloalkyl, alkaryl or aralkylgroup having up to twelve carbon atoms and wherein at least six of theR' groups are hydrogen atoms, as shown in U.S. Pat. No. 3,169,945. Thepolycaprolactone polyols that are used are shown by the formula on theright hand side of the equation; they can have an average molecularweight of from 200 to about 6,000. The preferred polycaprolactone polyolcompounds are those having an average molecular weight of from about 290to about 6,000, most preferably from about 290 to 3,000. The mostpreferred are the polycaprolactone diol compounds having an averagemolecular weight of from about 290 to about 1,500 and thepolycaprolactone triol and tetrol compounds having an average molecularweight of from about 290 to about 3,000; these are most preferredbecause of their low viscosity properties. In the formula m is aninteger representing the average number of repeating units needed toproduce the compound having said molecular weights. In the formula x isan integer having an average value of from about 2 to 8, preferably 2 to4. The hydroxyl number of the polycaprolactone polyol can be from about15 to 600, preferably from 200 to 500; and the polycaprolactone can havean average of from 2 to 8, preferably 2 to 4, hydroxyl groups.

Illustrative of polycaprolactone polyols that can be used in preparingthe adduct compositions of this invention, one can mention the reactionproducts of a polyhydroxyl compound having an average from 2 to 8hydroxyl groups with caprolactone. The manner in which these typepolycaprolactone polyols is produced is shown in U.S. Pat. No. 3,169,945and many such compositions are commercially available. In the followingtable there are listed illustrative polycaprolactone polyols. The firstcolumn lists the organic functional initiator that is reacted with thecaprolactone and the average molecular weight of the polycaprolactonepolyol is shown in the second column. Knowing the molecular weights ofthe initiator and of the polycaprolactone polyol one can readilydetermine the average number of molecules of caprolactone (CPL Units)that reacted to produce the compounds; this figure is shown in the thirdcolumn.

    ______________________________________                                        POLYCAPROLACTONE POLYOLS                                                                           Average  Average No.                                                          MW of    of CPL units                                    Initiator            polyol   in molecules                                    ______________________________________                                         1 Ethylene glycol   290      2                                                2 Ethylene glycol   803      6.5                                              3 Ethylene glycol   2,114    18                                               4 Propylene glycol  874      7                                                5 Octylene glycol   602      4                                                6 Decalene glycol   801      5.5                                              7 Diethylene glycol 527      3.7                                              8 Diethylene glycol 847      6.5                                              9 Diethylene glycol 1,246    10                                              10 Diethylene glycol 1,998    16.6                                            11 Diethylene glycol 3,526    30                                              12 Triethylene glycol                                                                              754      5.3                                             13 Polyethylene glycol (MW 200)*                                                                   713      4.5                                             14 Polyethylene glycol (MW 600)*                                                                   1,398    7                                               15 Polyethylene glycol (MW 1500)*                                                                  2,868    12                                              16 1,2-Propylene glycol                                                                            646      5                                               17 1,3-Propylene glycol                                                                            988      8                                               18 Dipropylene glycol                                                                              476      3                                               19 Polypropylene glycol (MW 425)*                                                                  835      3.6                                             20 Polypropylene glycol (MW 1000)*                                                                 1,684    6                                               21 Polypropylene glycol (MW 2000                                                                   2,456    4                                               22 Hexylene glycol   916      7                                               23 2-Ethyl-1,3-hexanediol                                                                          602      4                                               24 1,5-Pentanediol   446      3                                               25 1,4-Cyclohexanediol                                                                             629      4.5                                             26 1,3-bis(hydroxyethyl)-benzene                                                                   736      5                                               27 Glycerol          548      4                                               28 1,2,6-Hexanetriol 476      3                                               29 Trimethylolpropane                                                                              590      4                                               30 Trimethylolpropane                                                                              750      5.4                                             31 Trimethylolpropane                                                                              1,103    8.5                                             32 Triethanolamine   890      6.5                                             33 Erythritol        920      7                                               34 Pentaerythritol   1,219    9.5                                             35 1,4-Butanediol    546      4                                               36 Neopentyl Glycol  674      5                                               ______________________________________                                         *Average molecular weight of glycol.                                     

The structures of the compounds in the above tabulation are obvious toone skilled in the art based on the information given. The structure ofcompound No. 7 is: ##STR4## wherein the variables r and q are integers,the sum of r+q has an average value of 3.7 and the average molecularweight is 527. The structure of compound No. 20 is: ##STR5## wherein thesum of r+q has an average value of 6 and the average molecular weight is1,684. This explanation makes explicit the structural formulas ofcompounds 1 to 36 set forth above.

Although not specifically mentioned above, it is appreciated that otherlactone based polyols can be used in preparing the adduct compositionsof this invention. Illustrative of other lactone based polyols includethose derived from beta-propiolactone, delta-valerolactone,zeta-enantholactone and the like including derivatives thereof such asgamma-methyl-delta-valerolactone and the like.

Examples of the monohydric alcohol in the acrylate or methacrylate ofthe monohydric alcohol include methanol, ethanol, propanol, isopropanol,n-butanol, isobutanol, t-butanol, cycloheyl alcohol, benzyl alcohol,octyl alcohol, 2-ethyl hexanol, lauryl alcohol, n-decanol, undecanol,cetyl alcohol, stearyl alcohol, methoxyethyl alcohol, ethoxyethylalcohol, butoxyethyl alcohol, polyethylene glycol monomethyl alcohol,polyethylene glycol monoetbyl alcohol, 2-hydroxy-3-chloropropane,dimethylamino alcohol, diethylamino alcohol, glycidol, 2-trimethoxysilylethanol, ethylene chlorohydrin, ethylene bromohydrin, 2,3-dibromopropanol, allyl alcohol, oleyl alcohol, epoxystearyl alcohol, phenol andnaphthol. Examples of the polyhydric alcohol thereof include ethyleneglycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol,1,5-pentanediol, hexanediol, heptanediol, octanediol, nonanediol,dodecanediol, neopentyl glycol, 1,10-decanediol, 2-butene-1,4-diol,2-n-butyl-2-ethyl propanediol, cycloheptanediol,1,4-cyclohexanedimethanol, 3-cyclohexene-1,1-diethanol, polyethyleneglycol (e.g., diethylene glycol, triethylene glycol), polypropyleneglycol (e.g., dipropylene glycol, tripropylene glycol), polystyreneoxide glycol, polytetrabydrofuran glycol, xylilenediol,bis(B-hydroxyethoxy)benzene, 3-chloro-1,2-propanediol,2,2-dimethyl-1,3-propanediol, decalindiol,1,5-dihydroxy-1,2,3,4-tetrahydronaphthalene,2,5-dimethyl-2,5-bexanediol, 2-ethyl-1,3-hexanediol,2-ethyl-2-(hydroxymethyl)-1,3-propanediol,2-ethyl-2-methyl-1,3-propanediol, 3-hexene-2,5-diol, hydroybenzylalcohol, 2-methyl-1,4-butanediol, 2-methyl-2,4-pentanediol,1-phenyl-1,2-ethanediol, 2,2,4,4-tetramethyl-1, 3-cyclobutanediol,2,3,5,6-tetramethyl-p-xylene-a,a-diol,1,1,4,4-tetraphenyl-2-butyn-1,4-diol, 1,1-bi-2-naphthol,dibydroxynaphthalene, 1,1-methylene-di-2-naphthol, biphenol,2,2-bis(4-hydroxyphenyl)butane, 1,1-bis(4-hydroxyphenyl)cyclohexane,bis(hydroxyphenyl)methane, catechol, resorcinol, 2-methylresorcinol,4-chlororesorcinol, pyrogallol, a-(1-aminoethyl)-p-hydroxybenzylalcohol, 2-amino-2-methyl- 1,3-propanediol,2-amino-2-ethyl-1,3-propanediol, 3-amino-1,2-propanediol,N-(3-aminopropyl)-diethanolamine, N,N-bis(2-hydroxyethyl)piperazine,1,3-bis(hydroxymethyl)urea, 1,2-bis(4-pyridyl)-1,2-ethanediol,N-n-butyldiethanolamine, diethanolamine, N-ethyldiethanolamine,3-mercapto-1,2-propanediol, 3-piperidine-1,2-propanediol,2-(2-pyridyl)1,3-propanediol, a- (1-aminoethyl)-p-hydroxybenzyl alcohol,glycerol, trimethylolethane, trimethylolpropane, pentaerythritol,dipentaerythritol, tripentaerythritol, sorbitol, glucose, a-mannitol,butanetriol, 1,2,6-trihydroxyhexane, 1,2,4-benzenetriol, triethanolamineand 2,2-bis-(hydroxymethyl)-2,2',2"-nitrilotriethanol. Among theseacrylates and methacrylates of monohydric and polyhydric alcohols,ethylene glycol diacrylate, ethylene glycol dimethacrylate, polyethyleneglycol diacrylate, polyethylene glycol dimethacrylate, pentaerythritoltriacryate, pentaerythritol trimethacrylate, pentaerythritoltetraacrylate, pentaerythritol tetramethacrylate, dipentaerythritolhexaacrylate, dipentaerythritol hexamethacrylate, dipentaerythritolpentaacrylate, dipentaerythritol pentamethacrylate, glyceroltriacrylate, glycerol trimethacrylate, trimethylolpropane triacrylate,trimethylolpropane trimethacrylate, trimethylolethane triacrylate,trimethylolethane trimethacrylate, neopentylglycol diacrylate,neopentylglycol dimethacrylate, sorbitol hesaacrylate, sorbitolhexamethacrylate, sorbitol pentaacrylate and sorbitol pentamethacrylateare particularly useful.

The epoxy resin and polyol is combined with a photoinitiator. Thephotoinitiator is capable of effecting cationic polymerization of theepoxy resin component when the initiator is exposed to ultravioletradiation or sufficient thermal energy. The photoinitiator is always inan amount sufficient to cure the resin of the balancing compound uponbeing exposed to ultraviolet light. The photoinitiator is chosen fromthe group consisting of onium salts and combinations thereof. Suitablephotoinitiators are the onium salts having the formulae:

    R.sub.2 I+MX.sub.n

    R.sub.3 S+MX.sub.n

    R.sub.3 Se+MX.sub.n

    R.sub.4 P+MX.sub.n

    R.sub.4 N+MX.sub.n

where radicals represented by R can be the same or different organicradicals from 1 to 30 carbon atoms, including aromatic carbocyclicradicals of from 6 to 20 carbon atoms which can be substituted with from1 to 4 monovalent radicals selected from C.sub.(1-8) alkoxy, C(₁₋₈)alkyl, nitro, chloro, bromo, cyano, carboxy, mercapto, and the like, andalso including aromatic heterocyclic radicals including, e.g., pyridyl,thiophenyl, pyranyl, and the like, and MX_(n) -- is a non-basic,non-nucleophilic anion, such as BF₄ --, PF₆ --, AsF₆ --, SbF6--, SbCl₆--, HSO4--, CIO₄ --, and the like, the iron salts, especially theFerrocenium class, such as Ferrocenium hexafluorophosphate, used with aperoxide or hydroperoxide. Useful peroxides include cumenehydroperoxide, benzoyl peroxide, tertiaryamyl hydroperoxide, dicumylhydroperoxide or tertiarybutyl hydroperoxide.

The preferred onium salts for use herein are the diaryliodonium salts.Examples of suitable diaryliodonium salts are disclosed, for example, inU.S. Pat. No. 4,832,201, which is incorporated herein by reference. Themost preferred of these salts is that having the formula: ##STR6##

Examples of specific preferred bis-diaryl iodonium salts include, forexample, bis(dodecyl phenyl)iodonium hexafluoroarsenate, and bis(dodecylphenyl) iodonium hexafluoroantimonate, are preferred. Most preferred ofthese iodonium salts is bis(dodecyl phenyl)iodoniumhexafluoroantimonate.

The photoinitiator suitable for use in the balancing compound of thisinvention also may be any one of the well known photoinitiators such asdescribed in, for example, U.S. Pat. Nos. 4,231,951; 4,256,828;4,138,255 and 4,058,401, which patents are incorporated herein byreference. Preferred photoinitiators include triarylsulfonium complexsalts as decribed in U.S. Pat. No. 4,231,951, aromatic sulfonium oriodonium salts of halogen-containing complex ions as described in U.S.Pat. No. 4,256,828; aromatic onium salts of Group VIa elements asdescribed in U.S. Pat. Nos. 4,058,401 and 4,138,255; aromatic oniumsalts of Group Va elements as described in U.S. Pat. No. 4,069,055. Suchsalts are commercially available as FC-508 and FC-509 (available fromMinnesota Mining and Manufacturing Company), and as UVE-1014 (availablefrom General Electric Company).

Examples of the photopolymerization initiator to be used in the presentinvention include a-diketones such as benzyl or diacetyl; acyloins suchas benzoin; acyloin ethers such as benzoin methyl ether, benzoin ethylether and benzoin isopropyl ether; thioxanthones such as thioxanthone,2,4-diethylthioxanthone, thioxanthone-1-sulfonic acid andthioxanthone-4-sulfonic acid; benzophenones such as benzophenone,6,4,-bis(dimethylamino)-benzophenone and 4,4',-bis(diethylamino)-benzophenone; acetophenones such as acetophonone,p-dimethylaminoacetophenone, a,a'-dimethoxyacetoxyacetophenone,2,2,-dimethoxy-2-phenylacetophenone, p-methoxyacetophenone and2-methyl-[4-(methylthio)-phenyl]-2-morpholino-1-propanone; quinones suchas anthraquinone 1,4-naphthoquinone, halogen compounds such as phenacylchloride, tribromomethylphenylsulfone andtris(trichloromethyl)-s-triadine; and peroxides such as di-t-butylperoxide.

These compounds can be used either alone as the photopolymerizationinitiator or a mixture of two or more of them as the photopolymerizationinitiating system. Examples of the photopolymerization initiating systeminclude the combination of 2,4,5-triarylimidazole dimer and2-mercaptobenzoxazole or leuco crystal violet, the combination of4,4-bis(dimethylamino)benzophenone and benzophenone or benzoin methylether as disclosed in U.S. Pat. No. 3,427,161, the combination ofbenzoyl-N-methyl naphtothiazoline and2,4-bis(trichloromethyl)-6,-4-methoxyphenyl triazole as disclosed inU.S. Pat. No. 4,239,850; and the combination of dimethylthioxanthone and4-dialkylaminobenzoate as disclosed in JP-A-57-23602.

These photopolymerization initiators or photopolymerization initiatingsystem may be used preferably in an amount of from about 0.1 to 4 partsby weight, more preferably from about 0.2 to 2 parts by weight, based onthe solid components of the liquid light-sensitive resin composition.When the amount of the same is less than about 0.1 part by weight, theresulting liquid light-sensitive resin composition has a poorsensitivity. When it exceeds about 4 parts by weight, on the other hand,the resulting liquid light-sensitive resin composition suffers from someproblems such as the precipitation of crystals or insufficient hardeningof the lower part.

Each of these photoinitiators useful in the balancing compound of theinvention includes an organic acid component. The organic acid componentforms a Lewis acid during the curing process.

The improved balancing compound of the invention also includes a fillercombined with the epoxy resin, polyol if any, and photoinitiator. Thefiller is in an effective amount to give the compound a specific gravityabove 1.1. Suitable fillers are not ultraviolet light opaque and aredispersed throughout the epoxy resin whereby the combination of theresin and the filler is homogeneous. The filler is chosen from the groupconsisting of quartz, silica, Pyrex, Flint and Crown glasses, andcombinations thereof. The silica can be fused silica, fumed silica orcrystalline silica. The glass may be in fiber form or particulate form.In all cases, the preferred filler is not UV-light opaque.

Some filler is used in all of the balancing compound as a thixotrope inan amount sufficient to maintain the filler and photoinitiator and resinin suspension and homogeneous. Thixotropes can also Be used to providethe improved balancing compound with the desired slump and to insurethat when a putty is used, the adhesion cohesiveness and wet strength ofthe putty is sufficient to adhere sufficiently and strongly to the rotorbeing balanced that it stays in position on rotating the rotor during adynamics balancing procedure. In specific embodiments, such can besubject to peripheral speeds of about 42 feet per second or theequivalent of rotation of 1,700 to 1,800 rpm. Those fillers useful asthixotropes in the invention are chosen from the group consisting ofquartz silica, Pyrex glass, fumed silica, fumed silica with surfacetreatments of chorosilane or siloxane, Flint and Crown glasses, andother fine powders. The fine powders such as talc, mica or silicondioxide, titanium dioxide, calcium carbonate, magnesium carbonate,barium carbonate, calcium sulfate, magnesium sulfate and barium sulfateare less preferred as they are not transparent to ultraviolet light.

In specific embodiments using transparent fillers, the bonding compoundof the invention surprisingly may cure faster than unfilled epoxy resinsas the filler is more transparent to ultraviolet light than the resin.

Photosensitizers are combined with the epoxy resin, the polyol, thephotoinitiator and the filler in the improved balancing compound of theinvention. Photosensitizers are in the compound in an effective amountto catalyze the photoinitiators or to convert visible light intoultraviolet light and in combination with the photoinitiatorsabove-mentioned to cure the resin of the compound at ambienttemperatures upon the application of ultraviolet light in less thanabout 30 seconds. Those photoinitiators which convert visible light toultraviolet light are chosen from the group consisting of pigments,photosensitizers and combinations thereof.

The photosensitizers are chosen from the group of peroxides, anthracene,perylene, acridine orange, acridine yellow, phosphine R, benzoflavin,setoflavin, aromatic hydrocarbons, benzophenone and derivatives thereof,esters of o-benzoylbenzoic acids, acetophenone and derivatives thereof,benzoin and benzoin ethers and derivatives thereof, xanthone andderivatives thereof, thioxanthone and derivatives thereof, disulfidecompounds, quinone compounds, halogenated hydrocarbons, amines, etc.

Typical examples of the aromatic hydrocarbon are benzene, benzene-d₆,toluene, p-xylene, fluorobenzene, chlorobenzene, bromobenzene,iodobenzene, naphthalene, 1 -methylnaphthalene, 2-methylnaphthalene,1-fluoronaphthalene, 1-chloronaphthalene, 2-chloronaphthalene,1-bromonaphthalene, 2-bromonaphthalene, 1 - iodonaphthalene, 2-iodonaphthalene, 1-naphthol, 2-naphthol, biphenyl, fluorene,p-terphenyl, acenaphthene, p-quaterphenyl, triphenylene, phenanthrene,azulene, fluoranthene, chrycene, pyrene, 1,2-benzpyrene, anthracene,1,2-benzanthracene, 9,10-dichloroanthracene, 9,10-dibromoanthracene,9,10-diphenylanthracene, perylene, tetracene, pentacene, benzyl, etc.

The benzophenone and the derivatives thereof may include, for example,benzophenone, 2,4-dimetbylbenzophenone, 2,4-dichlorobenzophenone,4,4'-bis(dimethylamino)benzophenone, etc.

The esters of o-benzoylbenzoic acids may include, for example, methylo-benzoylbenzoate, ethyl o-benzoylbenzoate, phenyl o-benzoylbenzoate,##STR7## etc.

The acetophenone and the derivatives thereof may include, for example,acetophenone, 4-methylacetophenone, 3-methylacetophenone,3-methoxyacetophenone, etc. The benzoin, the benzoin ethers and thederivatives of these may include, for example, benzoin, benzoin methylether, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-butylether, benzoin triphenylsilyl ether, ##STR8## etc.

The xanthone and the derivatives thereof may include, for example,xanthone, 2,4-dimethylxanthone, 2,4-dichloroxanthone, etc.

The thioxanthone and the derivatives thereof may include, for example,isopropylthioxanthone, thioxanthone, 2,4-dimethylthioxanthone,2,4-dichlorothioxanthone, etc.

The disulfide compounds may include, for example: ##STR9##

The quinone series compounds may include, for example, benzoquinone,naphthoquinone, anthraquinone, 5,12-naphthacene dione, 2,7-pyrene dione,etc.

The halogenated hydrocarbons may include, for example, carbontetrachloride, hexachloroethane, carbon tetrabromide, ##STR10## etc.

The amines may include for example, diphenyl amine, carbazole,triphenylamine, ##STR11## etc.

Other photosensitizers may include, for example, propiophenone,anthrone, benzaldehyde, butylophenone, 2-naphthylphenylketone,2-naphthaldehyde, 2-acetonaphthone, 1-naphthylphenylketone,1-acetonaphthone, 1-naphthoaldehyde, fluorenone, 1-phenyl-1,2-propanedione, benzonitorile, acetone, biacetyl, acridine orange, acridine,Rhodamine-B, eosine fluorescein, ##STR12## etc.

The photosensitizers exemplified above may be used alone or incombination, and should be mixed preferably in an amount of from 0 to 5parts by weight, more preferably, 0.01 to 5 parts by weight, based onthe epoxy resin component.

The use of photosensitizers to convert visible light to ultravioletlight depends upon the exposure and light source to be used in photohardening the balancing compound of the invention. These light sourcesmay include a low pressure mercury lamp, moderate pressure mercury lamp,or a high pressure mercury lamp, an ultra-high pressure mercury lamp, axenon lamp, a metal halide lamp or combinations thereof.

A wetting agent is also used in combination with the epoxy resin, thephotoinitiator and the filler of the improved balancing compound of theinvention. Sufficient wetting agent is used to reduce the surface energyof the resin of the balancing compound to a level that all of the filleris wet with the resin. It is imperative that the resin completely wetthe filler to minimize or preferably eliminate the refraction orreflection of ultraviolet light at the resin/filler interface. Suchrefraction and reflection is paramount to an unwanted opaqueness of thecompound. Any opaqueness of the compound inhibits the cure of the resinof the compound. Wetting agents are chosen from the group consisting ofhydrocarbons, silicones, florochemicals and other surfactants andcombinations thereof. Useful silicones include mythoxyterminatedpolydimethylsiloxanes, butoxyterminated polydimethylsiloxanes, andhydroxyterminated polydimethylsiloxanes. Useful fluoro-chemicals includeammonium perfluoroalkyl sulfonates, potassium perfluoroalkyl sulfonates,amine perfluoroalkyl sulfonates, fluorinated alkyl amphoteric mixture,potassium fluorinated alkyl carboxylates, fluorinated alkyl quaternaryammonium iodides, ammonium perfluoroalky carboxylates, fluorinated alkylpolyoxyethylene ethanols, fluorinated alkyl alkoxylate, fluorinatedalkyl esters. Useful hydrocarbons include the acrylics such as PC1244sold by Monsanto Company of St. Louis, Mo.

Catalysts are also used in combination with the epoxy resin, polyol,photoinitiator, filler, pigments and photo sensitizers, wetting agent,thixotrope in the improved balancing compound of the invention. Thesecatalysts are used in combination with the photoinitiator and the resinto cure the resin at ambient temperatures upon the application ofultraviolet light at the concentration and time of incidence required.These catalysts include copper salt catalysts, hydroperoxide catalystsand combinations thereof. Such catalysts as copper salt catalysts can bea copper halloid, bromide chloride or copper styrate, copper glutonate,copper citrate, copper napthalate and the lie or combinations thereof.

The preferred amine triflates that can be used as catalysts in thepresent invention include

CF₃ SO₃ H.N(C₆ H₅), CF₃ SO₃ H.NH₃,

CF₃ SO₃ H.CH₃ NH₂,CF₃ SO₃ H.(CH₃)₃ N,

CF₃ SO₃ H.CH₂ H₅ NH₂,

CF₃ SO₃ H.(C₂ H₅)₂ NH,

CF₃ SO₃ H.(C₂ H₅)₃ N,

CF₃ SO₃ H.(iP--C₃ H₇)₂ NH,

CF₃ SO₃ H.(i--C₃ H₇)₂ N(C₂ H₅),

CF₃ SO₃ H.(i--C₃ H₇)₂ N(C₂ H₄ OH),

CF₃ SO₃ H.H₂ N(C₂ H₄ OH),

CF₃ SO₃ H.HN(C₅ H₈ O),

CF₃ SO₃ H.H₂ NC(CH₃)₂ CH₂ OH,

CF₃ SO₃ H.HN(C₆ H₁ l),

CF₃ SO₃ H.HN(C₂ H₄ OH)₂,

CF₃ SO₃.(CH₃)₄ N and the like, including mixtures thereof.

Preferred metal salts of sulfonic acid which can be used as catalysts inthe present invention include the metal salts of

CF₃ SO₃ H,

C₈ F₁ 7SO₃ H, CF₃ C₆ F₁ 0SO₃ H,

C₃ F₇ SO₃ H, C₂ F₅ SO₃ H, C₂ HF₄ SO₃ H,

C₃ F₇ CHFCF₂ SO₃ H,(CF₃)₂ CHCF₂ SO₃ H,

C₄ F₇ SO₃ H, (CF₃)₂ CF(CF₂)₄ SO₃ H,

C₄ F₉ CFHCF₂ SO₃ H,

C₃ H₇ CH(CF₃)CF₂ SO₃ H, C₁ 1F₂ 3SO₃ H,

C₅ H₁ 1CFHCF₂ SO₃ H, C₇ F₁ 5CFHCF₂ SO₃ H, and the like, includingmixtures thereof. Representative of the metal cat ions of such metalsalts are those of the metals lithium, sodium, potassium, magnesium,calcium, strontium, barium, yitrium, vanadium, manganese, cobalt,nickel, copper, silver, zinc, cadmium, mercury, lead, bismuth, tungsten,lanthanum, neodymium, tin and gadolinium.

Other sulfonic acids and their derivatives can also be used to preparethe adducts of the present invention and include para-toluene sulfonicacid, dinonylnaphthylene sulfonic acid, alkyl sulfonic acids and thelike.

The sulfonic acid metal salts used in this invention can be prepared bysimply neutralizing the sulfonic acid precursors with a metal oxide,hydroxide, or carbonate or metal salt. The amino and ammonium salts canbe formed by neutralization of the sulfonic acids with a salt-formingprimary, secondary or tertiary amine, ammonia, or quaternary ammoniumhydroxide. These latent forms of the sulfonic acid catalysts can beactivated by heating them in the presence of the polycaprolactone polyoland polyepoxide to generate the sulfonic acid in its free acid form tomake it available for catalyzing the reaction.

The sulfonic acid catalysts and derivatives thereof can be used inamounts varying from about 1 ppm to about 10,000 ppm or even greater(from about 0.0001 parts percent to about 5.0 parts based on the resin.The preferred concentration of sulfonic acid catalyst and derivativesthereof ranges from about 5 ppm to about 5,000 ppm (from about 0.0005parts to about 0.5 parts Based on the resin). The most preferredconcentration of sulfonic acid catalyst and derivatives thereof used inthis invention ranges from about 50 ppm to about 4,000 ppm (from about0.005 parts to about 0.4 parts based on the resin).

The most preferred sulfonic acid catalysts and derivatives thereofuseful in preparing the adduct compositions of the present inventioninclude diethylammonium triflate, trifluoromethanesulfonic acid,ammonium triflate, di-isopropyl-ethyl ammonium triflate and di-isopropylammonium triflate. Some of these catalysts are commercially availablefrom the 3M Company.

Thermohardening catalysts can also be used. These thermohardeningcatalysts for catalyzing the thermal reaction of the epoxy group, knownepoxy-hardening accelerators may be used. Examples include amines, forexample, aliphatic primary amines, for example, polyamines such asdiethylenetriamine, triethylenetetramine, tetraethylenepentamine,iminobispropylamine (dipropyltriamine), bis(hexamethylenetriamine and1,3,6-trisaminomethylhexane, polymethylenediamines such astrimethylhexamethylenediamine, polyetherdiamine anddiethylaminopropylamine, and alicyclic polyamines such asmenthenediamine, isophoronediamine,bis(4-amino-3-methylcyclohexyl)methane and N-aminoethylpiperazine,aromatic primary amines such as methaphenylenediamine,diaminophenylmethane, diamininophenylsulfone and eutectic mixtures ofaromatic diamines, modified amines such as polyamine epoxy resinadducts, polyamine-ethylene oxide adduct, polyamine-propylene oxideadduct, cyanoethylated polyamine and ketoimine; secondary amines such aspiperidine, piperazine and morpholine; and tertiary amines such astetramethylguanidine, triethanolamine, benzyldimethyl-amine and2,4,6-tris(dimethylaminomethyl)phenol; acid anhydrides, for example,aromatic acid anhydrides such as phthalic anhydride, trimelliticanhydride, ethylene glycol bis(anhydrotrimellitate), glyceroltris(anhydrotrimellitate), pyromellitic anhydride and3,3',-4,4'-benzophenone tetracarboxylic anhydride; alicyclic acidanhydrides such as maleic anhydride, succinic anhydride,tetrahydrophthalic anhydride, methyltetrahydro phthalic anhydride,endometbylenetetrahydrophthalic anhydride,methylendomethylenetetrahydrophthalic anhydride, alkenylsuccinicanhydride, hexahydrophthalic anhydride, methylhexahydrophthalicanhydride and methylcyclobexenetetracarboxylic anhydride; aliphatic acidanhydrides such as polyadipic anhydride, polyazelaic anhydride andpolysebacic anhydride; and halogenated acid anhydrides such aschlorendic anhydride and tetrabromophthalic anhydride; imidazolecompounds such as 2-methylimidazole, 2-ethyl-4-methylimidazole,2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole,1-benzyl-2-methylimidazole, 1-cyanoethyl-2-metbylimidazole,1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole,1-cyanoethyl-2-undecylimdazo trimellitate,1-cyanoethyl-2-phenylimidazolium trimellitate, 2-metbylimidazoliumisocyanurate, 2-phenylimidazolium isocyanurate,2,4-diamino-6-[2-methylimidazolyl-(1)]ethyl-S-triazine,2,4-diamino-6-[2-ethyl-1)]-ethyl-S-triazine,2,4-diamino-6-[2-undecylimidazolyl-(1)-ethyl-S-triazine,2-phenyl-4-methyl-5-hydroxymethylimidazole,2-phenyl-4,5-dihydroxyrethylimidazole,1-cyanoethyl-2-phenyl-4,5-di(cyanoethoxy-methyl)imidazol e,1-dodecyl-2-methyl-3-benzylimidazolium chloride and1,3-dibenzyl-2-methylimidazolium chloride; phenols such as novolak typephenol resins, cresol type phenol resins, resorcinol type phenol resinsand polyvinylphenol; Lewis acid/amine complexes such as borontrifluoride/amine complex, boron pentafluoride/amine complex and arsenicpentafluoride/amine complex, dicyandiamides such as dicyandiamide,o-tolylbiguanide, phenylbiguanide and a-2,5-dimethylbiguanide, organicacid hydrazides such as succinic acid hydrazide, adipic acid hydrazide,isophthalic acid hydrazide and p-oxybenzoic acid hydrazide;diaminomaleonitrile derivatives such as diaminomaleonitrile and benzyldiaminomaleonitrile, melamine derivatives such as melamine andN,N-diarylmelamine, amineimide derivatives and polymercaptanes.

One of these thermohardening catalysts or a mixture thereof may be usedpreferably in an amount of from about 0.01 to 10 parts by weight, morepreferably from about 0.05 to 5 parts by weight, based on 100 parts byweight of the resin component of the liquid light-sensitive resincomposition. When the amount of the same is less than about 0.01 part byweight, the resulting film shows an insufficient strength. When itexceeds about 10 parts by weight, on the other hand, the resultingliquid light-sensitive resin composition suffers from some problems suchas precipitation of crystals or a decrease in the stability of theliquid.

The following examples of the improved balancing compound of theinvention will be better understood.

EXAMPLE 1

A balancing compound of the invention was formulated by mixing 100 partsof a bisphenol-A epoxy resin (DER 331 from Dow Chemical Company,Midland, Mich.) with 3.0 parts of a florinated wetting agent (FC-171from Minnesota Mining & Mfg., Inc. of Minneapolis, Minn.) and 12 partsof a fumed silica filler (Cabosil 720TS from Cabot Laboraties, Inc. ofBoston, Mass.) and 1.5 parts of an onium salt photoinitiator (FX-512from Minnesota Mining & Mfg., Inc. of Minneapolis, Minn.). The resin,wetting agent, filler and photoinitiator were intimately mixed to form apaste.

The balancing composition was placed upon a rotor to be Balanced, thebalancing composition not being sufficiently tacky, adherent or cohesiveto adhere to the rotor during dynamic testing before curing, thebalancing composition having no slump at room temperature, and aspecific gravity above 1.1. The rotor was exposed to ultraviolet light(10 nm to about 400 nm) of less than about 40 watts per squarecentimeter for about 30 seconds.

The rotor was dynamically tested and determined to be balanced. Therotor was spin tested at 15,000 rpm at a temperature of 300° F. for 30seconds to determine whether or not the Balancing compound was fullycured. The balancing compound was fully cured. The rotor was thendynamically tested again. The rotor was in balance.

EXAMPLE 2

A balancing compound of the invention was formulated by mixing 50 partsof cycloalphatic resin and 20 parts of Hexadecane resin (UVR6105 andUVR6212, respectively from Union Carbide Corporation, Danbury, Conn.)with 2.5 parts of a silicone wetting agent (L-7604 from Union CarbideCorporation of Danbury, Conn.) and 30 parts Caprolactone triol (UVR0310from Union Carbide Corporation of Danbury, Conn.) and 1 part of an oniumsalt photoinitiator (UVI6990 from Union Carbide Corporation of Danbury,Conn.) and 200 parts of 100 mesh filler (Fused Quartz, from varioussuppliers, and 0.3 parts isopropylthioxanthone sensitizer (ITX fromBiddle-Sawyer). The resins, wetting agent, filler, photoinitiator, trioland sensitizer were intimately mixed to form a paste.

The balancing composition was placed upon a rotor to be balanced, thebalancing composition not being sufficiently tacky, adherent or cohesiveto adhere to the rotor during dynamic testing before curing, thebalancing composition having no slump at room temperature, and aspecific gravity above 1.1. The rotor was exposed to ultraviolet light(10 nm to about 400 nm) of less than about 40 watts per squarecentimeter for about 30 seconds. The rotor was dynamically tested anddetermined to be balanced. The rotor was spin tested at 15,000 rpm at atemperature of 300° F. for 30 seconds to determine whether or not thebalancing compound was fully cured. The balancing compound was fullycured. The rotor was then dynamically tested again. The rotor was inbalance.

EXAMPLE 3

A balancing compound of the invention was formulated by mixing 80 partsof cycloalphatic and cresol novolac resins (CY-179 and ECN,respectively, from Ciba-Geigy) with 0.01 parts of acrylic wetting agent(PC-1244 from Monsanto Company of St. Louis, Mo.) and 1.5 partsferrocenium salt photoinitiator (Irgacure 261 from Ciba-Geigy) and 300parts of -325 mesh filler (quartz powder available from varioussuppliers) and isopropylthioxanthone and cumenebydroperoxide sensitizers(ITX by Biddle-Sawyer and CHP by Atochem, respectively). The resins,wetting agent, filler, photoinitiator and sensitizers were intimatelymixed to form a putty.

A sufficient amount of putty was applied to the rotor to balance therotor. The putty had a specific gravity above 1.1. The putty had noslump at room temperature. The putty was sufficiently tacky, adherentand cohesive to adhere to the rotor during dynamic testing. The rotorwas dynamically tested. The rotor was not in balance. A small amount ofputty was removed from the rotor. The rotor was again tested forbalance. The rotor was in balance. The putty was cured by exposing therotor to ultraviolet light (about 10 nm to about 400 nm) for about 40watts per square centimeter for about 30 seconds. The cure of thebalancing compound was tested by spin testing the rotor at 15,000 rpm at300° F. for 30 seconds. The rotor was dynamically tested for balance.The rotor was in balance.

EXAMPLE 4

A balancing compound of the invention was formulated by mixing 100 partsof a bisphenol-A expoxy resin (Epon 828 from Shell Chemical) with 1.0part of a fluorinated wetting agent (FC-171 from Minnesota Mining &Mfg., Inc. of Minneapolis, Minn.) and 2.0 parts onium saltphotoinitiator (UVI-6990 from Union Carbide Corporation of Danbury,Conn.) and 320 parts of -325 mesh filler (quartz powder, available fromvarious suppliers) and an anthracene sensitizer (Anthracene by AldrichChemical). The resin, wetting agent, filler, photoinitiator andsensitizer were intimately mixed to form a putty.

A sufficient amount of putty was applied to the rotor to balance therotor. The putty had a specific gravity above 1.1. The putty had noslump at room temperature. The putty was sufficiently tacky, adherentand cohesive to adhere to the rotor during dynamic testing. The rotorwas dynamically tested. The rotor was not in balance. A small amount ofputty was removed from the rotor. The rotor was again tested forbalance. The rotor was in balance. The putty was cured by exposing therotor to ultraviolet light (about 10 nm to about 400 nm) for about 40watts per square centimeter for about 30 seconds. The cure of thebalancing compound was tested by spin testing the rotor at 15,000 rpm at300° F. for 30 seconds. The rotor was dynamically tested for balance.The rotor was in balance.

EXAMPLE 5

A balancing compound of the invention was formulated by mixing 90 partsof cycloaliphatic epoxy resin (UVR6110 from Union Carbide Corporation ofDanbury, Conn.) with 1.0 parts of silicone wetting agent (Silwet L-7604from Union Carbide Corporation of Danbury, Conn.) and 1.5 parts oniumsalt photoinitiator (UVI6990 from Union Carbide Corporation of Danbury,Conn.) and 250 parts of -100 mesh filler (fused quartz, available fromvarious suppliers) and 10 parts caprolactone epoxy triol (UVR0310 fromUnion Carbide Corporation of Danbury, Conn.) and 4.0 parts fumed silicathixotrope (Cabosil 720TS from Cabot Laboratories of Boston, Mass.). Theresin, wetting agent, filler, photoinitiator, triol and thixotrope wereintimately mixed to form a paste.

The balancing composition was placed upon a rotor to be balanced, thebalancing composition not being sufficiently tacky, adherent or cohesiveto adhere to the rotor during dynamic testing before curing, thebalancing composition having no slump at room temperature, and aspecific gravity above 1.1. The rotor was exposed to ultraviolet light(10 nm to about 400 nm) of less than about 40 watts per squarecentimeter for about 30 seconds. The rotor was dynamically tested anddetermined to be balanced. The rotor was spin tested at 15,000 rpm at atemperature of 300° F. for 30 seconds to determine whether or not thebalancing compound was fully cured. The balancing compound was fullycured. The rotor was then dynamically tested again. The rotor was inbalance.

The improved balancing compound of the invention is a single part epoxybased composition which can be applied to a rotor as either a paste or aputty, does not require mixing prior to use, cure rapidly at roomtemperature, has a long shelf life, and meets all of the objects of theinvention.

While a specific embodiment of the invention has Been shown anddescribed herein for purposes of illustration, the protection affordedby any patent which may issue upon this application is not strictlylimited to the disclosed embodiment; but rather extends to allstructures and arrangements which fall fairly within the scope of theclaims which are appended hereto:

What is claimed is:
 1. A method of balancing a rotor which comprisesapplying to the rotor a balancing composition which comprises an epoxyresin, a photoinitiator in an amount sufficient to cause cationicpolymerization and cure said resin upon the application of ultravioletlight (about 10 nm to about 400 nm), and a filler in an amount to givesaid composition a specific gravity above 1.1, said filler not beingultraviolet light opaque and selected from a group consisting of quartz,silica, and the combination thereof, and exposing the balancingcomposition at ambient temperature to ultraviolet light of less than 40watts per square centimeter for less than 30 seconds and curing saidresin.
 2. The method of claim 1 wherein said resin is selected from thegroup consisting of bisphenol-A, bisphenol-F, novolak, difunctionalglycidol ester, and cycloaliphatic based epoxy resins, and combinationsthereof.
 3. The method of claim 1 wherein said resin consists of about13% to about 90% weight of said composition.
 4. The method of claim 1wherein said composition further comprises a polyol up to about 100parts per 100 parts of said resin.
 5. The method of claim 4 wherein saidpolyol is chosen from the group consisting of polycaprolactone alcohols,polyether alcohols, polyester alcohols, other monofunctional alcohols,other difunctional alcohols, other trifunctional alcohols, andcombinations thereof.
 6. The method of claim 1 wherein said compositionis homogeneous.
 7. The method of claim 1 wherein, said photoinitiator ispresent from about 0.1 to about 4 parts per 100 of said resin.
 8. Themethod of claim 1 wherein said photoinitiator initiator is selected fromthe groups consisting of onium salts, iron salts, and combinationsthereof.
 9. The method of claim 1 wherein said photoinitiator isselected from the group consisting of organic compounds having an acidcomponent, wherein said acid component forms a Lewis acid during theresin curing process.
 10. The method of claim 1 wherein said compositionfurther comprises a wetting agent sufficient to reduce the surfaceenergy of said resin to a level that said filler is wet with said resin.11. The method of claim 10 wherein said wetting agent is selected fromthe group consisting of hydrocarbon, silicone, fluorochemical, and othersurfactants and combinations thereof.
 12. The method of claim 10 whereinsaid wetting agent is present in an amount from about 0.001 to about 1.0parts per 100 of said resin.
 13. The method of claim 1 furthercomprising a wetting agent in an amount sufficient to minimizerefraction and reflection of ultraviolet light at the resin/fillerinterface.
 14. The method of claim 1 wherein said filler is present inan amount sufficient to maintain said photoinitiator in suspension andsaid composition homogeneous.
 15. The method of claim 14 wherein saidfiller is present in an amount less than 20 parts per 100 of said resin.16. The method of claim 1 wherein said composition further comprises acatalyst which in combination with said photoinitiator will cure saidresin at ambient temperatures upon the application of ultraviolet lightof less than 40 watts per square centimeter in less than about 30seconds.
 17. The method of claim 16 wherein said catalyst is selectedfrom the group consisting of copper salt and hydroperoxide catalysts andcombinations thereof.
 18. The method of claim 16 wherein said catalystsare present in an amount from about 0.01 to about 5 parts per 100 ofsaid resin.
 19. The method of claim 1 wherein said resin when cured iscross-linked through said epoxy groups.
 20. The method of claim 1wherein said composition has no slump at room temperature, issufficiently tacky, adherent and cohesive to adhere to the rotor duringdynamic testing before curing, said method comprising, prior to the stepof exposing, the step of dynamically testing the rotor with saidbalancing composition in position thereon and adjusting the amount ofbalancing composition on the rotor to achieve balance.
 21. The method ofclaims 20 wherein the amount and position of the balancing compositionis adjusted and dynamic testing of the rotor is repeated until thedesired degree of balance is attained before the resin is cured.
 22. Themethod of claim 20 wherein said adjusting step includes adjusting boththe amount and the position of the balancing composition on the rotorand dynamically retesting the rotor until the desired degree of balanceis attained.
 23. The method of claim 1 further comprising, after thestep of exposing, the step of dynamically testing the rotor with thebalancing composition in position thereon.
 24. A method of balancing arotor comprising applying to a rotor a balancing composition comprisingan epoxy resin, a photoinitiator in an amount to cure said resin atambient temperature upon the application of ultraviolet light (about 10nm to about 400 nm) of less than 40 watts per square centimeter in lessthan about 30 seconds, and a filler in an amount to give saidcomposition no slump at room temperature and a specific gravity above1.1, the composition not being sufficiently tacky, adherent or cohesiveto adhere to the rotor during dynamic testing before curing, curing saidresin by exposing said composition to ultraviolet light of less than 40watts per square centimeter for less than about 30 seconds, dynamicallytesting the rotor with the now cured balancing composition in positionthereon, adding an additional amount of the balancing composition on therotor to achieve the desired balance, if required, and then curing saidadditional resin.
 25. The method of claim 24 wherein said adjusting stepincludes adjusting both the amount and position of the balancingcomposition on the rotor.
 26. The method of claim 24 wherein said resinis chosen from the group consisting of bisphenol-A, bisphenol-F,novolak, difunctional glycidol ester, and cycloaliphatic based epoxyresins, organosilicon moners having a six member silicon dioxide ring,and sulfur containing moners having three and four member sulfurcontaining rings, and combinations thereof.
 27. The method of claim 24wherein said resin consists of about 13% to about 90% weight of saidcomposition.
 28. The method of claim 24 wherein said compositioncomprises a polyol up to about 100 parts per 100 parts of said resin.29. The method of claim 28 wherein the Union Carbide R value of saidpolyol is less than
 3. 30. The method of claim 28 wherein said polyol isselected from the group consisting of polycaprolactone alcohols,polyether alcohols, polyester alcohols, other monofunctional alcohols,other difunctional alcohols, other trifunctional alcohols, andcombinations thereof.
 31. The method of claim 24 wherein said filler isnot ultraviolet light opaque.
 32. The method of claim 24 wherein saidfiller is selected from the group consisting of quartz, silica, Pyrex,Flint and Crown glasses, and combinations thereof.
 33. The method ofclaim 24 wherein said composition wets said filler.
 34. The method ofclaim 24 wherein said composition is homogeneous.
 35. The method ofclaim 24 further comprising a photoinitiator in an amount sufficient tocure said resin upon being exposed to ultraviolet light.
 36. The methodof claim 35 wherein said photoinitiator is present from about 0.1 toabout 4 parts per 100 of said resin.
 37. The method of claim 35 whereinsaid photoinitiator initiator is selected from the groups consisting ofonium salts, iron salts and combinations thereof.
 38. The method ofclaim 35 wherein said photoinitiator is selected from the groupconsisting of organic compounds having an acid component, wherein saidacid component forms a Lewis acid during the resin curing process. 39.The method of claim 24 further comprising an effective amount of aphotosensitizer to convert visible light into ultraviolet light.
 40. Themethod of claim 24 wherein said photosensitizer is present in an amountless than 5.0 parts per 100 of said resin.
 41. The method of claim 24further comprising a wetting agent sufficient to reduce the surfaceenergy of said resin to a level that said filler is wet with said resin.42. The method of claim 41 wherein said wetting agent is selected fromthe group consisting of hydrocarbon, silicone, fluorochemical, and othersurfactants and combinations thereof.
 43. The method of claim 41 whereinsaid wetting agent is present in an amount from about 0.001 to about 1.0parts per 100 of said resin.
 44. The method of claim 41 furthercomprising a wetting agent in an amount sufficient to minimizerefraction and reflection of ultraviolet light at the resin/fillerinterface.
 45. The method of claim 24 wherein said filler is present inan amount sufficient to maintain said photoinitiator in suspension andsaid composition homogeneous.
 46. The method of claim 45 wherein saidfillers are chosen from the group consisting of quartz, silica, Pyrex,Flint and Crown glasses, and combinations thereof.
 47. The method ofclaim 45 wherein said filler is present in an amount less than 20 partsper 100 of said resin,
 48. The method of claim 24 further comprising acatalyst which in combination with said photoinitiator will cure saidresin at ambient temperatures upon the application of ultraviolet light(about 10 nm to about 400 nm) of less than 40 watts per squarecentimeter in less than about 30 seconds.
 49. The method of claim 48wherein said catalyst is selected from the group consisting of coppersalt and hydroperoxide catalysts and combinations thereof.
 50. Themethod of claim 48 wherein said catalysts are present in an amount fromabout 0.01 to about 5 parts per 100 of said resin.
 51. The method ofclaim 24 wherein said resin when cured is cross-linked through saidepoxy groups.